I really loved the characterisation, and the way they came up with some really clever and deeply intricate stories and ideas. Acting was top notch: not a bad performance to be seen. Most of the art (particularly the backgrounds) were gorgeous. Some of the earlier songs were just brilliant :)
On to the moaning, I have always been bugged by their storyboard-driven arcs, because I feel like that leads to 90% buildup and then only 10% payoff most of the time. eg Peridot's arc was really good, whereas the Diamonds; Spinel and even Steven just felt rushed IMO because much more time was spent building up than actually resolving.
My partner suggested (which I think would have been AMAZING) having Steven's meltdown halfway-ish through Future. That way we spend almost as much time with him during the resolution, instead of (another...) flash-forward where things are Groovy Because Therapy. But it's a kid's show afterall 🤷♀️